Short-circuiting device for electric motors



Sept. 20, 1938. 3 D, HARTQG 2,130,883

SHORT CIRCUITING DEVICE FOR ELECTRIC MOTORS Filed Dec. 28, 1936 F/g. Z

Patented Sept. 20, 1938 UNITED STATES PATENT OFFICE SHORT-CIRCUITING DEVICE FOR ELEC- TRIO MOTORS Application December 28, 1936, Serial No. 117,765

This specification, aided by the accompanying drawing, discloses certain new and useful improvements in short-.circuiting devices for alternating current motors.

The purpose and use of short-circuiting devices are well known and adequately described in the art to which such devices relate, and further reiteration would only be additional surplusage except, briefly summarized, an electric motor short-circuiting device or operating changing device is the means employed to convert an alternating current motor automatically from that of a repulsion starting condition to that of an induction running condition, and vice versa, as the revolutions per minute of the rotor shaft increase or decrease.

The improvements hereinafter described and illustrated are primarily directed to simplification of construction employing few working parts in the structure, improved means and mode of operation, reduced production cost, and a construction having the advantageous feature of a compact and complete assembly unit.

An object is to provide a short-circuiting device centrifugally operated to effectuate instantly a make and break contact with the commutator, combined with a rolling action on the commutator within the sweep of the circuiters motion.

Another object is to provide an electric motor short-circuiting or current-changing device in which the circuiters, while operating under centrifugal influence, move oscillatory with a cushioning smoothness superinduced by means of a resilient spring pressure yieldingly operative on the circuiters at a position of maximum effectiveness; and a further object is to provide electric motor short-circuiters that engage and contact with the commutator at one position, then, upon increasing speed, sweep to a different radial position, thus insuring a clean, bright electrical conducting surface on the face of the commutator and the short-circuiters.

Possessed of the capacity to fulfill such ends, the invention consists in novel features of construction which embody a rotatable body having a peripheral contour providing means to engage short-circuiters for operative movement thereon, a plurality of short-circuiters mounted for operative movement and engagement on the peripheral contour of the expressed body, and means-yieldingly operating upon the short circuiters.

For the purpose more clearly to understand the embodied improvements constituting the invention, the following description is given, and, with the aid of the accompanying drawing, it is discernible:

Fig. 1 is an elevation in section of the commutator end of an electric motor.

Fig. 2 is an elevation in section of a portion of the commutator end of an electric motor.

Fig. 3 is an elevation in section of a portion of the electrical short-circuiting assembly unit.

Fig. 4 is a view in elevation of a circular or garter spring member.

Fig. 5 is a face view of an apertured disc.

Fig. 6 is a fragmentary surface view in elevation.

Fig. '7 is a view in dotted outline illustrating the manner in which the short-circuiters are assembled on the rotatable body.

In the drawing, l designates the rotor shaft of an electric motor to which is attached a commutator hub ll having a plurality of segmental commutator bars I2 mounted upon its circumferential surface. Located adjacent the lateral face l3 of the huh I I and in spaced relation therewith is that of a rotatable body denominated a flanged disc l4, having a central hub l and a rim l6 providing peripheral contours ll, 3 and I9.

Upon the rim surface thus provided, a plurality of segmental short-circuiters 20 are mounted for operative movement. Formed upon the body of the short-circuiters 20 and depending for a limited distance therefrom are projecting portions 2| and 22 of which one portion 22 is provided with a claw or hook 23 which is adapted to engage the peripheral contour of the rim H5 at [9 in order to secure the short-circuiters in engaged position while in operation. The projecting portions 2| and 22 are spaced one from the other by an opening or cutout formed in the body 20 of the short-circuiters to provide surfaces 24, 25 and 26 suitable for mounting the shortcircuiters 20 upon the peripheral contour of the rim IS.

The body 20 also has an additional opening or cutout in order to provide surfaces 21, 28 and 29. The surfaces thus provided and enumerated constitute means contributory to the manner of assembling the short-circuiters, their maintenance operatively, and their operative performance.

In the drawing (Fig. '7) there is shown the manner in which the short-circuiters are assembled on the flanged disc I4. As shown, the shortcircuiter 20 is positioned longitudinally with its opening in line with the projecting rim I6, then turned clockwise until the surface 24 of the shortcircuiter is brought into contact with the surface of the flanged disc M and the surface of the claw 23 in contact with the surface of the rim 19. The short-circuiter then assumes an upright or vertical position. Thus positioned, it is incapable of dislocation while in operation, and otherwise immovable other than in the direction to contact with the commutator l2. In the manner thus indicated, the short-circuiters 20 are assembled upon the peripheral contour of the flanged disc E4 in series, a definite number of which are assembled between spacers 3i], portions which are pressed from and bent to a rectangular position, and projecting a limited distance from the plane surface of the flanged disc I4.

In the form and embodiment of the invention illustrated in Fig. 1, it is there shown that the flanged disc M is mounted securely on the rotor shaft I0, and that it is positioned in spaced relation to the commutator. The short-circuiters are shown in an upright or vertical position, and they are sustained in that normal operative position by means of a resiliently yielding coil spring 3!. The coil spring is shown to have one end face seated against the surface 28 of the short-circuiters, and the other end face abutting the wall face I3 of the hub H.

In order to maintain the short-circuiting device in its proper position on the shaft is, a chan nel 32 is formed in the shaft. The location of the channel in the shaft is such that one side wall 33 of the channel is in line with the face of the flanged disc [4. Into the channel thus formed and provided, an aperture'd disc 34, fitting tightly into the channel and pressed securely therein, arranges the entire unit in complete operative assembly. Thus equipped, the rotor shaft 10 when in action assumes certain speed revolutions per minute and, upon the attainment of a definite speed, the short-circuiters are impelled to action under centrifugal influence. The shortcircm'ters being so designed and constructed respond to the centrifugal influence by turning on their axis or pivot 35 (indicated in the drawing Fig. 1 and Fig. 3) under the cushioningly yielding influence of the spring 3! to contact with the commutator i2, thereby changing the electrical conditions of the motor. The initial contact of the short-circuiters upon the surface of the commutator is made at a position indicated at 36, then changing to a position indicated at 3?, in consequence of increased speed. At the instance of reduction of the speed below definite revolutions per minute, the centrifugal influence is overcome by the pressure influence of the spring 3| and by means of which the short-circuiters are restored to their normal position.

In the view Fig. 2 of the drawing, a different form of spring is shown in assembly with the short-circuiters 20. The spring 3! is circular in form and exerts its influence in such a manner as to be diametrically expansive and contractive. The spring 38 is shown seated within the opening of the short-circuiters and bearing upon the surface 27, thereby sustaining the short-circuiters in contact with the peripheral contour ll of the rim 16. When affected by centrifugal influence, the short-circuits are drawn off their seat and instantly swept into contact on the face of the commutator [2 at a position indicated at 35 and, at the instance of increased speed, advance radially outward on the face of the commutator to a position indicated at 37!. As the short-circuiters are advancing radially outward under centrifugal influence, their axis or pivot is acting likewise and along the surface 24 of the projecting portion 2|, their radial movement outward being limited as shown in dotted outline by the engagement of the claw 23 with the rim surface l9.

In the drawing, Fig. 3 is a view in section of a portion of the present short-circuiting device denominated an assembly unit. This construction provides for the employment (all other conditions being equal) of a disc 40 having a hub 4| apertured to fit tightly upon and be fixed to the surface of the hub l5. It is obvious that the disc iil is employed to provide an abutment for the end face of the coil spring 3| and, in so doing, the device is complete as an assembly unit. This type of construction possesses an advantage in that it tends to facilitate transportation, replacement sales, and is appreciably economical and convenient in assembly with electric motors.

In order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific details shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into eifect, and the invention is, therefore, claimed in any and all of its forms and modifications within the legitimate and valid scope of the appended claims.

I claim and desire to secure by Letters Patent of the United States of America my invention which is:

1. In an alternating current motor having a commutator, a short-circuiting device for shortcircuiting the commutator, comprising a hubflanged disc having a peripheral contour terminating in a rim, a plurality of short-circuiters each having projecting body portions spaced one from the other by an opening therebetween, the opening therebetween providing the means whereby the short-circuiters are capable of being mounted for operative movement astride the peripheral contour of the hub-flanged disc, the short-circuiters thus mounted being capable of oscillatory movement upon the peripheral contour of the hub-flanged disc in a direction to and from the commutator only, means on the projecting body portions of the short-circuiters adapted to restrain their displacement while operative under centrifugal influence, and pressure means yieldingly operative upon and in contact with the short-circuiters, the named pressure means, having contact with the short-circuiters and localized between the short-circuiters commutator contacting surface and the surface upon which the short-circuiters pivot.

2. In a short-circuiting device for electric m0- tor cominuta'tors, the short-circuiting device comprising a rotatory support a series of commutator short-circuiters mounted upon the peripheral contour of the rotatory support, each short-circuiter having body portions providing projecting limbs, the projecting limbs of each short-circuiter being structurely capable of embracing the peripheral contour of the rotatory support in a way to enable the short-circuiters to form operative engagement upon the rotatory support while under the influence of centrifugal force and spring pressure means interposed between the short-circuiters and the radial face of the commutator yieldingly sustaining the short-circuiters in normal position upon the rotatory support.

STEPHEN D. HAR'I'OG. 

